Wheelchairs are used to provide mobility to disabled individuals. Conventional wheelchairs comprise a generally tubular frame with a seat. A backrest may also be attached to the rear of the frame. A pair of larger wheels is mounted to the rear of the frame, while smaller, castered wheels are attached to the front of the frame. Often, the castered wheels are welded or bolted to the frame such that replacement (either permanently or temporarily) with other castered wheels is difficult. For example, larger diameter castered wheels allow for easier rolling of the wheelchair over soft terrain. However, if the castered wheels are already welded or bolted to the frame, it becomes impractical to switch the castered wheels when travel over soft terrain is expected. A footrest is also commonly provided at the front of the wheelchair.
Several types of non-folding wheelchairs currently exist, and these can be considered to be rigid wheelchairs with frames designed generally to be light and stiff for easier wheeling and more efficient rolling. One typical element of conventional rigid wheelchair frames is a transverse (tubular) member that spans the width of the frame near or at the location where the rear wheels are mounted. This transverse member may serve to provide a frame element for attachment of the rear wheels. As well, the transverse member provides a strengthening and stiffening component to the wheelchair frame structure.
More recent developments in wheelchair design have provided for the easy adjustability of various aspects of the wheelchair to suit the size and needs of the users. For example, it is sometimes desirable for the user to sit lower in the wheelchair at an increased “dump” position (i.e. where the back of the seat is lowered with respect to the front of the seat). This is especially the case when wheeling, as the user is in a more stable position and able to wheel more efficiently. On other occasions, it may be desirable to be able to elevate the seat above the normal sitting position. This may be helpful when the user needs to access countertops or shelves. Similarly, the position and angle of the backrest may also be adjusted depending on the needs of the users.
However, the mechanisms that allow for the adjustability of the seat and the backrest may physically interfere with other components in the wheelchair frame. Of particular concern is the transverse member. As this member spans the width of the frame at the location of the rear wheels and is located directly beneath the seat, this member may limit the degree of movement and adjustability of the seat. For example, U.S. Pat. No. 7,845,665 to Borisoff also discloses a wheelchair with a seat assembly that is adjustable relative to the frame. The adjustment is made using a pair of gas springs that suspend the seat assembly from below. However, the frame in Borisoff also comprises a transverse tubular member connected near the rear end of the frame. This tubular member stiffens the frame but also limits the adjustability of the seat.
U.S. Patent Publication No. 2010/0038880 to Bagg discloses a wheelchair with an adjustable seat assembly to accommodate users of different sizes. For example, the seat width, the seat height, and the angle of the seat may be adjusted in accordance with the characteristics or the size of the users. However, the front castered wheels and the footrest are permanently connected together to form a unitary front assembly, which is then attached to the front of the frame. In the event that the user wishes to exchange the castered wheels with a different set of wheels, it is necessary to replace the entire front assembly.
The present invention addresses the need for a wheelchair frame that is sufficiently strong to accommodate the weight of a user while at the same time allowing for increased range of adjustments of the components. The present invention also addresses the need for a wheelchair frame that allows for the easy interchangeability of various components of the wheelchair.